Laminated leaf valve and shock absorber

Abstract

A laminated leaf valve (V) according to the present invention is laminated on a valve seat member (1) having a port (1c) and opens and closes the port (1c). The laminated leaf valve (V) comprises: an annular first leaf valve (2) having a through-hole (2a) to be connected to the port (1c); an annular second leaf valve (3) superposed on the back surface of the first leaf valve (2); and an annular third leaf valve (4) superposed on the back surface of the second leaf valve (3). The second leaf valve (3) is provided with: a plurality of connection holes (3a) that are provided apart from each other in the circumferential direction and that can be connected to the plurality of through-holes (2a); a plurality of cutout chokes (3b) that each open from the outer circumference serving as a free end and that are connected to the corresponding connection holes (3a); and fragile parts (3d) that reduce the rigidity of arms (3c) that are outer circumferential parts of a corresponding one of the connection holes (3a) and are formed on both sides of a corresponding cutout passage (3b) in the circumferential direction.

Description

Stacked leaf valves and shock absorbers

[0001] The present invention relates to stacked leaf valves and shock absorbers.

[0002] A shock absorber is used, for example, by being interposed between the body and axle of a vehicle in order to improve the ride comfort of the vehicle, and suppresses vibration of the body and wheels by the damping force it exerts when expanding and contracting.

[0003] Such a shock absorber includes, for example, a cylinder, a piston rod movably inserted into the cylinder, a piston slidably inserted into the cylinder to divide the interior of the cylinder into an extension-side chamber and a compression-side chamber, a free piston slidably inserted into the cylinder to divide an air chamber below the compression-side chamber in the cylinder, a port provided in the piston to connect the extension-side chamber and the compression-side chamber, and a stacked leaf valve placed on top of the piston to open and close the port.

[0004] The stacked leaf valve has its inner periphery fixed to the piston rod and overlapped on the piston to close the port, and opens the port by deflecting its outer periphery when pressure is applied upstream of the port.

[0005] In such stacked leaf valves, when the piston moves slowly relative to the cylinder, it may be desirable to build up a damping force proportional to the piston velocity, in which case a choke passage may be provided.

[0006] Specifically, as disclosed in JP 11-294515A, for example, a stacked leaf valve equipped with a choke passage comprises: a first leaf valve of an annular shape which is stacked directly on the piston and which has an arc-shaped through-hole facing the port; a second leaf valve of an annular shape which has the same inner and outer diameter as the first leaf valve and which is stacked on the side opposite the piston of the first leaf valve; the ...nular shape which has a plurality of arc-shaped communicating holes which communicate with the through-hole and notched passages which open from the outer periphery and which communicate with the communicating holes; and a third leaf valve of an annular shape which has the same inner and outer diameter as the first and second leaf valves and which is stacked on the side opposite the piston of the second leaf valve.

[0007] By sandwiching the second leaf valve between the first leaf valve and the third leaf valve, the stacked leaf valve closes the port while communicating the port with the outside of the stacked leaf valve via the through hole, the communication hole, and the notched passage, and the notched passage forms a choke or orifice.

[0008] In a laminated leaf valve configured in this manner, when the piston moves at a low speed, it does not bend and remains seated on the valve seat formed on the piston and surrounding the port, but a damping force can be generated by passing the hydraulic oil through the notched passage.

[0009] JPH11-294515A

[0010] In this way, in a stacked leaf valve, the second leaf valve has a plurality of arc-shaped communicating holes arranged at equal intervals around the circumference, and a plurality of cutout passages that open from the outer periphery and communicate with each of the communicating holes.Since the communicating holes must be connected to the through holes of the first leaf valve, the circumferential length of the communicating holes is made as long as possible to ensure communication between the communicating holes and the through holes.

[0011] In the second leaf valve, the notched passage opens at the center of the arc-shaped communicating hole, and arc-shaped elongated arms are formed on both sides of the notched passage at the outer periphery of the communicating hole. Therefore, if the circumferential length of the communicating hole is increased as described above, the length of the arms extending from the circumferential ends of the communicating hole to the notched passage will necessarily increase.

[0012] As a result, when the second leaf valves are transported or stored, the arms of the adjacent second leaf valves may become entangled with each other, for example, by getting into the communicating holes of the adjacent second leaf valves, which requires a lot of effort to untangle and separate the entangled second leaf valves when assembling the stacked leaf valves.

[0013] On the other hand, if the circumferential length of the communicating hole is shortened to shorten the circumferential length of the arms, it is possible to prevent the arms of the second leaf valve from becoming entangled with each other, but the shortened length of the arms increases the bending rigidity of the arms, making them less likely to deform.As a result, when the second leaf valve is sandwiched between the first and third leaf valves, the arms are less likely to come into close contact with the first and third leaf valves, creating gaps between the arms and the first and third leaf valves, which causes the choke and orifice characteristics of the cutout passages to not be exhibited as intended.

[0014] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a laminated leaf valve and a shock absorber that can be easily assembled and that can provide good choke characteristics.

[0015] In order to solve the above problems, the stacked leaf valve of the present invention is annular, with either the inner or outer periphery being a free end so that flexing on the free end side is permitted, and is stacked on a valve seat member having a port to open and close the port, and comprises: an annular first leaf valve having a through hole communicating with the port; an annular second leaf valve stacked on the anti-seat side that forms the back surface of the first leaf valve; and an annular third leaf valve stacked on the anti-seat side that forms the back surface of the second leaf valve, and the second leaf valve has a plurality of communication holes spaced apart in the circumferential direction and capable of communicating with the through holes, a plurality of notched passages that open from the free end and lead to the corresponding communication holes, and fragile portions that reduce the rigidity of the arms formed on the outer periphery of the communication holes on at least one side of the circumferential direction of the notched passages.

[0016] In a stacked leaf valve configured in this manner, the arm portion of the second leaf valve has a weak portion with low rigidity, making it easy to bend and deform, and can fit tightly to both the first leaf valve and the third leaf valve without creating a gap between them, thereby preventing the communication hole from communicating with the operating chamber through any means other than the notched passage. Furthermore, because the arm portion has a weak portion, it can fit tightly to both the first leaf valve and the third leaf valve, so the circumferential length of each communication hole in the second leaf valve can be narrowed, reducing the workload when assembling the stacked leaf valve.

[0017] FIG. 1 is a longitudinal sectional view of a shock absorber to which a stacked leaf valve according to one embodiment of the present invention is applied. FIG. 2 is an enlarged sectional view of a stacked leaf valve according to one embodiment of the present invention. FIG. 3(a) is a plan view of a first leaf valve in a stacked leaf valve according to one embodiment of the present invention. FIG. 3(b) is a plan view of a second leaf valve in a stacked leaf valve according to one embodiment of the present invention. FIG. 3(c) is a plan view of a third leaf valve in a stacked leaf valve according to one embodiment of the present invention. FIG. 4 is a plan view of a second leaf valve in a stacked leaf valve according to a first modified example of the present invention. FIG. 5 is a plan view of a second leaf valve in a stacked leaf valve according to a second modified example of the present invention. FIG. 6 is a plan view of a second leaf valve in a stacked leaf valve according to a third modified example of the present invention.

[0018] The present invention will be described below based on the embodiments shown in the drawings. As shown in Figure 1, a stacked leaf valve V in one embodiment is applied to the piston portion of a shock absorber D. The stacked leaf valve V is annular, with its outer periphery as a free end, allowing for deflection on the free end side, and is stacked on a piston 1 serving as a valve seat member having a compression-side port 1c as a port, to open and close the compression-side port 1c. The stacked leaf valve V also includes a first annular leaf valve 2 having a through-hole 2a communicating with the compression-side port 1c, a second annular leaf valve 3 stacked on the back surface of the first leaf valve 2 on the side opposite the piston, and a third annular leaf valve 4 stacked on the back surface of the second leaf valve 3 on the side opposite the piston.

[0019] 1, a shock absorber D to which a laminated leaf valve V is applied includes a cylinder 10 as an outer tube, a rod 11 movably inserted into the cylinder 10, a piston 1 as a valve seat member connected to the rod 11 and inserted axially movably into the cylinder 10 to divide the interior of the cylinder 10 into two working chambers, an expansion-side chamber R1 and a compression-side chamber R2, and a laminated leaf valve V. This shock absorber D is used by being interposed between the body and axle of a vehicle (not shown), and suppresses vibrations of the vehicle body and wheels.

[0020] Hereinafter, each part of the stacked leaf valve V and the shock absorber D will be described in detail. First, each part of the shock absorber D will be described. As shown in Fig. 1 , the shock absorber D includes a cylindrical cylinder 10 with a bottom as an outer tube, a rod 11 movably inserted into the cylinder 10, and a piston 1 as a valve seat member connected to the rod 11 and movably inserted into the cylinder 10, which divides the interior of the cylinder 10 into an expansion-side chamber R1 and a compression-side chamber R2 as working chambers.

[0021] A bracket (not shown) is provided at the base end of the rod 11, which is the upper end in Fig. 1, and the rod 11 is connected to one of the vehicle body and the axle via the bracket (not shown). A bracket (not shown) is also provided at the bottom 10a of the cylinder 10, and the cylinder 10 is connected to the other of the vehicle body and the axle via the bracket (not shown).

[0022] In this way, shock absorber D is interposed between the vehicle body and the axle. When the vehicle travels on an uneven road surface and the wheels vibrate up and down relative to the vehicle body, rod 11 moves in and out of cylinder 10, expanding and contracting shock absorber D, and piston 1 moves up and down (axially) within cylinder 10.

[0023] The shock absorber D also includes an annular rod guide 13 that closes the upper end of the cylinder 10 and through which the rod 11 is slidably inserted, forming an enclosed space inside the cylinder 10. A free piston 14 is slidably inserted into the cylinder 10 on the opposite side of the piston 1 from the rod 11.

[0024] A liquid chamber L is formed above the free piston 14 in the cylinder 10, and an air chamber G is formed below it. The liquid chamber L is further divided by the piston 1 into an extension-side chamber R1 on the rod side and a compression-side chamber R2 on the piston side, and the extension-side chamber R1 and the compression-side chamber R2 are each filled with a liquid. The liquid filled in the shock absorber D may be hydraulic oil, water, an aqueous solution, or other liquid. On the other hand, compressed air or a gas such as nitrogen gas is sealed in the air chamber G.

[0025] When the rod 11 retracts from the cylinder 10 during extension of the shock absorber D, the free piston 14 moves upward within the cylinder 10 in accordance with the volume of the retracted rod 11, expanding the air chamber G and compensating for the volume of the rod 11 retracted from the cylinder 10. Conversely, when the shock absorber D retracts, the rod 11 enters the cylinder 10, and the free piston 14 moves downward within the cylinder 10 in accordance with the volume of the entered rod 11, contracting the air chamber G and compensating for the volume of the rod 11 entering the cylinder 10. Note that instead of the free piston 14, a bladder, bellows, or the like may be used to separate the liquid chamber L and the air chamber G, and the configuration of the movable partition that serves as this partition can be changed as appropriate.

[0026] As described above, in this embodiment, the shock absorber D is a single-rod, single-cylinder shock absorber. When the shock absorber D extends or retracts, the free piston (movable partition) 11 expands or contracts the air chamber G to compensate for the volume of the rod 11 moving in and out of the cylinder 10. However, the configuration for this volume compensation can also be modified as appropriate. For example, if the free piston 14 and the air chamber G are eliminated and an outer tube is provided outside the cylinder 10, and a reservoir for storing liquid and gas is formed between the cylinder 10 and the outer tube to make the shock absorber a twin-cylinder shock absorber, the reservoir may be used to compensate for the volume of the rod 11 moving in and out of the cylinder 10. Note that the reservoir may be formed in a tank separate from the cylinder 10. The shock absorber D may also be configured as a double-rod shock absorber in which the piston 14 is attached to the center of the rod 11 and the ends of the rod 11 protrude from both ends of the cylinder 10.

[0027] The rod 11 has a reduced outer diameter at the tip end, and includes a small diameter portion 11a having a small outer diameter at the tip end, a large diameter portion 11b having an outer diameter larger than that of the small diameter portion 11a and provided above the small diameter portion 11a in FIG. 1, a step portion 11c provided at the boundary between the small diameter portion 11a and the large diameter portion 11b, and a threaded portion 11d provided on the outer periphery of the tip end of the small diameter portion 11a.

[0028] 1, the piston 1 serving as a valve seat member is annular and fitted onto the outer periphery of the small diameter portion 11a of the rod 11, and is fixed to the rod 11 by a piston nut 15 that is screwed onto a threaded portion 11d of the rod 11. The piston 1 is also assembled to the rod 11, and the outer periphery of the piston 1 is in sliding contact with the inner periphery of the cylinder 10, dividing the interior of the cylinder 10 into an expansion-side chamber R1 and a compression-side chamber R2 that serve as working chambers.

[0029] 2 , a plurality of expansion-side ports 1b are provided in the main body 1a, opening from the lower end of the main body 1a in FIG. 2 and leading to the outer periphery at the upper end in FIG. 2 , a plurality of compression-side ports 1c as ports opening from the upper end of the main body 1a in FIG. 2 and leading to the outer periphery at the lower end in FIG. 2 , a ring-shaped seat portion 1d protruding downward from the lower end of the main body 1a in FIG. 2 and surrounding the outer periphery of the expansion-side port 1b, and a ring-shaped seat portion 1e protruding upward from the upper end of the main body 1a in FIG. 2 and surrounding the outer periphery of the compression-side port 1c.

[0030] As described above, the main body 1a is annular, and its outer periphery is in sliding contact with the inner periphery of the cylinder 10. In addition to the seat portions 1d and 1e, the main body 1a is provided with an inner periphery seat portion 1f at its lower end, which protrudes downward from the inner periphery of the lower opening end of the expansion-side port 1b, and an inner periphery seat portion 1g at its upper end, which protrudes upward from the inner periphery of the upper opening end of the compression-side port 1c, as shown in Fig. 2 .

[0031] Eight expansion-side ports 1b are provided at equal intervals in the circumferential direction of the main body portion 1a, and each expansion-side port 1b opens between the inner seat portion 1f and the seat portion 1d at the lower end of the main body portion 1a in FIG. 2, extends obliquely upward, and opens at the outer periphery of the seat portion 1e at the upper end of the main body portion 1a in FIG. 2, thereby connecting the expansion-side chamber R1 and the compression-side chamber R2. Note that a plurality of expansion-side ports 1b are provided at equal intervals in the circumferential direction of the main body portion 1a. Furthermore, the expansion-side ports 1b are expansion-side ports that allow liquid to flow from the expansion-side chamber R1 to the compression-side chamber R2 when the shock absorber D is extended.

[0032] The compression-side port 1c as a port opens between the inner peripheral seat portion 1g and the seat portion 1e at the upper end of the main body portion 1a in FIG. 2, extends downward in the axial direction, and opens at the outer periphery of the seat portion 1d at the lower end of the main body portion 1a in FIG. 2, thereby connecting the expansion-side chamber R1 and the compression-side chamber R2. The compression-side ports 1c are provided in the main body portion 1a in a number of eight, the same as the expansion-side ports 1b, at equal intervals in the circumferential direction of the main body portion 1a. The compression-side ports 1c are compression-side ports that allow liquid to flow from the compression-side chamber R2 to the expansion-side chamber R1 during contraction of the shock absorber D. The number of the expansion-side ports 1b and the compression-side ports 1c provided on the piston 1 can be arbitrarily changed in design. Furthermore, the expansion-side ports 1b and the compression-side ports 1c may be provided along the axial direction of the main body portion 1a as long as they are surrounded by the corresponding seats 1d and 1e, respectively.

[0033] In this embodiment, the seat portion 1d is provided at the lower end of the main body portion 1a in FIG. 2 and is formed by an annular protrusion protruding downward from the lower end of the main body portion 1a. It surrounds the outer periphery of the expansion-side port 1b and functions as an expansion-side valve seat. On the other hand, the seat portion 1e is provided at the upper end of the main body portion 1a in FIG. 2 and is formed by an annular protrusion protruding upward from the upper end of the main body portion 1a. It surrounds the outer periphery of the compression-side port 1c and functions as a compression-side valve seat. It is sufficient that the seat portions 1d and 1e surround the respective ports 1b and 1c and function as valve seats. Depending on the arrangement of the respective ports 1b and 1c relative to the main body portion 1a, the seat portions 1d and 1e may be petal-shaped and connected to the inner periphery seat portions 1f and 1g to independently surround the respective ports 1b and 1c.

[0034] Next, the stacked leaf valve V includes a first annular leaf valve 2 having a through hole 2a connected to the compression side port 1c, a second annular leaf valve 3 overlapped on the side opposite the piston that forms the back surface of the first leaf valve 2, and a third annular leaf valve 4 overlapped on the side opposite the piston that forms the back surface of the second leaf valve 3.

[0035] 2 , which is the expansion-side chamber side of the piston 1 serving as a valve seat member, and is fixed to the outer periphery of the small diameter portion 11 a of the rod 11 together with the piston 1, with the inner periphery being the fixed end and the outer periphery being the free end, allowing for deflection on the outer periphery side. In this embodiment, the laminated leaf valve V includes a plurality of leaf valves that are annular and have an outer diameter smaller than that of the third leaf valve 4 and are stacked on the back surfaces of the three leaf valves, the first leaf valve 2, the second leaf valve 3, and the third leaf valve 4, so that the outer diameters of the leaf valves gradually decrease. However, the leaf valves stacked on the back surfaces of at least the first leaf valve 2, the second leaf valve 3, and the third leaf valve 4 may be eliminated, or the number of leaf valves stacked may be changed.

[0036] Furthermore, above the stacked leaf valve V in FIG. 2, there are stacked a spacer 5 whose outer diameter is smaller than that of the uppermost leaf valve of the stacked leaf valve V, and an annular valve stopper 6 whose outer diameter is approximately the same as that of the first leaf valve 2. When the stacked leaf valve V is fixed to the small diameter portion 11a of the rod 11 together with the spacer 5, the stacked leaf valve V can bend with the outer peripheral edge of the spacer 5 as a fulcrum, and if the amount of bending becomes too great, the stacked leaf valve V will come into contact with the valve stopper 6, restricting further bending and preventing deterioration due to excessive bending.

[0037] When the stacked leaf valves V are stacked on the upper end of the piston 1 in FIG. 2, the lowermost first leaf valve 2 in FIG. 2 abuts against the inner circumferential seat portion 1g and the seat portion 1e, thereby closing the upper opening end in FIG. 2, which is the outlet end of the compression side port 1c.

[0038] Furthermore, when the laminated leaf valve V receives pressure from the compression-side chamber R2 acting through the compression-side port 1c and bends its outer periphery to separate from the seat portion 1e, it opens the compression-side port 1c, allowing the liquid to flow from the compression-side chamber R2 to the expansion-side chamber R1 through the gap between the compression-side port 1c and the seat portion 1e, while providing resistance to the flow. In this way, the laminated leaf valve V functions as a compression-side damping valve that opens and closes the compression-side port 1c to provide resistance to the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1.

[0039] The first leaf valve 2, the second leaf valve 3, and the third leaf valve 4 all have the same inner diameter and outer diameter. As shown in Fig. 3, the first leaf valve 2 is annular and has arc-shaped through-holes 2a spaced apart in the circumferential direction in a range facing between the inner circumferential seat portion 1g and the seat portion 1e of the piston 1 as viewed in the axial direction. When the first leaf valves 2 are stacked at the upper end of the piston 1 in Fig. 2, the through-holes 2a face between the inner circumferential seat portion 1g and the seat portion 1e and communicate with the compression-side port 1c. Note that a plurality of through-holes 2a may be provided lined up in the circumferential direction.

[0040] 3, the second leaf valve 3 is annular and includes three arc-shaped communication holes 3a spaced apart in the circumferential direction in an area facing the inner circumferential seat portion 1g and the seat portion 1e of the piston 1 when viewed in the axial direction, three notched passages 3b opening from the outer periphery as a free end and leading to the center of the corresponding communication hole 3a, arm portions 3c formed on the outer periphery of the communication holes 3a on both sides of the notched passages 3b in the circumferential direction, and weakened portions 3d that reduce the rigidity of the arm portions 3c. The third leaf valve 4 is annular and does not include any holes, as shown in FIG.

[0041] When the second leaf valve 3 is stacked on the rear surface of the first leaf valve 2, opposite the side of the piston, and the third leaf valve 4 is stacked on the rear surface of the second leaf valve 3, the second leaf valve 3 is sandwiched between the first leaf valve 2 and the third leaf valve 4, and the communication hole 3a faces the through hole 2a of the first leaf valve 2, and the communication hole 3a communicates with the compression-side port 1c via the through hole 2a. Furthermore, the communication hole 3a is blocked at its upper side by the third leaf valve 4 stacked on the second leaf valve 3, so that the communication hole 3a communicates with the expansion-side chamber R1 only via the notched passage 3b. Furthermore, the notched passage 3b is blocked at its top and bottom by the first leaf valve 2 and the third leaf valve 4, forming an elongated choke passage that communicates the communication hole 3a with the expansion-side chamber R1. Although the first leaf valve 2, second leaf valve 3, and third leaf valve 4 have the same outer diameter, this can be changed as desired as long as, when the second leaf valve 3 is sandwiched between the first leaf valve 2 and the third leaf valve 4, the communication hole 3a is connected to the outer periphery of the stacked leaf valve V only by the notched passage 3b and the notched passage 3b functions as a choke passage by covering the top and bottom of the notched passage 3b. In this embodiment, the notched passage 3b functions as a choke passage, but may also function as an orifice instead. In this embodiment, the communication hole 3a is arc-shaped, but it may be linear as long as it is aligned in the circumferential direction.

[0042] The arm portions 3c are formed on the outer periphery of the communicating holes 3a on both circumferential sides of the notched passages 3b by providing a plurality of communicating holes 3a that are spaced apart circumferentially in the second leaf valve 3 and notched passages 3b that open from the outer periphery of the second leaf valve 3 and communicate with the corresponding communicating holes 3a. The arm portions 3c are on the outer periphery of the communicating holes 3a and extend from the circumferential ends of the communicating holes 3a to the notched passages 3b, and their circumferential length varies depending on the circumferential length of the communicating holes 3a. Therefore, the circumferential length of the arm portions 3c increases as the circumferential length of the communicating holes 3a increases, and decreases as the circumferential length of the communicating holes 3a decreases.

[0043] In the stacked leaf valve V of this embodiment, the second leaf valve 3 has notches 3e, 3e that open from both circumferential ends of the communication hole 3a and extend toward the outer periphery, which is the free end, and the notches 3e, 3e form portions where the radial width of the arm portion 3c narrows on the outer periphery side of the communication hole 3a of the second leaf valve 3, and these portions function as weakened portions 3d, reducing the bending strength of the arm portion 3c. Thus, in this embodiment, the second leaf valve 3 has weakened portions 3d formed by the notches 3e, 3e that lead to the communication hole 3a in each arm portion 3c. Therefore, the provision of the weakened portions 3d makes it easier for the arm portion 3c, on the notch passage side, which is the tip, to bend from the weakened portions 3d. In the stacked leaf valve V of this embodiment, the cutout passage 3b is connected to the center of the communication hole 3a, and arm portions 3c are formed on the outer periphery of the communication hole 3a on both circumferential sides of the cutout passage 3b. However, the cutout passage 3b may be connected to the circumferential end of the communication hole 3a, and arm portions 3c may be provided on only one circumferential side of the cutout passage 3b. In this case, a cutout 3e opening from the opposite circumferential side of the communication hole 3a from the cutout passage 3b may be provided to provide a fragile portion 3d.

[0044] Next, the extension-side leaf valves 7 are stacked below the piston 1 in FIG. 1. The extension-side leaf valves 7 are laminated leaf valves formed by stacking a plurality of annular plates, and are stacked at the lower end of the piston 1 in FIG. 2 as a valve seat member, and are fixed to the outer periphery of the small diameter portion 11a of the rod 11 together with the piston 1. The inner periphery of the lowermost annular plate of the extension-side leaf valve 7 abuts against the inner periphery seat portion 1f, and the inner periphery side fixed to the rod 11 is the fixed end, and the outer periphery side is the free end. Therefore, the extension-side leaf valve 7 is allowed to bend in a direction away from the piston 1 on the outer periphery side, which is the free end side, and the outer periphery side is seated on and removed from the seat portion 1d.

[0045] When the outer peripheral side of the extension-side leaf valve 7 is seated on the seat portion 1d, it is in close contact with the inner peripheral seat portion 1f and the seat portion 1d, blocking the outlet end of the extension-side port 1b that opens between the inner peripheral seat portion 1f and the seat portion 1d. When the free end is bent by pressure from the extension-side port 1b side and separated from the seat portion 1d, it opens the extension-side port 1b and provides resistance to the flow of liquid passing through the gap that is generated between it and the seat portion 1d.

[0046] The valve stopper 6, spacer 5, stacked leaf valve V, piston 1, and extension-side leaf valve 7 configured in this manner are assembled in this order to the outer periphery of the small diameter portion 11 a of the rod 11, and then are fixed to the rod 11 by being sandwiched between the piston nut 15, which is screwed to the threaded portion 11 d of the small diameter portion 11 a, and the step portion 11 c of the rod 11.

[0047] The laminated leaf valve V and shock absorber D are configured as described above, and their operation will be described below. First, when the shock absorber D performs an extension operation and the piston 1 moves upward in Figure 1 relative to the cylinder 10, the upward movement of the piston 1 in Figure 1 causes the liquid in the expansion-side chamber R1, which is compressed, to bend the expansion-side leaf valve 7 and pass through the expansion-side port 1b and move to the compression-side chamber R2. Furthermore, during the extension operation of the shock absorber D, the laminated leaf valve V closes and seats on the seat portion 1e, but the compression-side port 1c is connected to the expansion-side chamber R1 through the through-hole 2a, the communication hole 3a, and the notched passage 3b, so that the liquid in the expansion-side chamber R1 can move to the compression-side chamber R2 through the choke passage formed by the notched passage 3b.

[0048] During the extension operation of the shock absorber D, when the piston speed is low and the pressure in the expansion-side chamber R1 does not reach the valve opening pressure of the expansion-side leaf valve 7, the liquid cannot pass through the expansion-side port 1b because the expansion-side port 1b is kept closed by the expansion-side leaf valve 7, and instead passes through the compression-side port 1c and the choke passage to move from the expansion-side chamber R1 to the compression-side chamber R2.

[0049] Therefore, when the shock absorber D is extending and the piston speed is low, the choke passage provides resistance to the flow of liquid from the extension-side chamber R1 to the compression-side chamber R2, and the shock absorber D generates a damping force that hinders the extension operation.

[0050] On the other hand, when the piston speed exceeds the low speed and becomes high speed during the extension operation of the shock absorber D, the pressure in the extension-side chamber R1 reaches the valve opening pressure of the extension-side leaf valve 7, causing the extension-side leaf valve 7 to bend and open. Then, the liquid passes through the extension-side port 1b and then passes between the extension-side leaf valve 7 and the seat portion 1d, moving from the extension-side chamber R1 to the compression-side chamber R2.

[0051] Therefore, when the shock absorber D is extended and the piston speed is high, the extension-side leaf valve 7 provides resistance to the flow of fluid from the extension-side chamber R1 to the compression-side chamber R2, and the shock absorber D generates a damping force that hinders the extension operation.

[0052] As described above, when shock absorber D extends, if the piston speed is low, it generates a damping force specific to a choke that rises in proportion to the piston speed, and if the piston speed is high, it generates a damping force specific to a leaf valve that increases in proportion to the piston speed, although the rate at which the damping force increases with respect to the piston speed is smaller than at low speeds. Note that as shock absorber D extends, free piston 14 rises in Figure 1 in accordance with the volume of rod 11 retracted from cylinder 10, expanding air chamber G and compensating for the volume of rod 11 retracted from cylinder 10.

[0053] On the other hand, when the shock absorber D contracts and the piston 1 moves downward in FIG. 1 relative to the cylinder 10, the downward movement of the piston 1 in FIG. 1 causes the liquid in the compression-side chamber R2 to bend the laminated leaf valve V and move through the compression-side port 1c to the expansion-side chamber R1.

[0054] Furthermore, when the shock absorber D is contracting, if the piston speed is low and the pressure in the compression-side chamber R2 does not reach the valve-opening pressure of the stacked leaf valve V, the stacked leaf valve V does not bend and remains seated on the seat portion 1e, so that the liquid passes through the compression-side port 1c and the choke passage and moves from the compression-side chamber R2 to the extension-side chamber R1.

[0055] Therefore, when the shock absorber D is contracting and the piston speed is low, the choke passage provides resistance to the flow of liquid from the compression-side chamber R2 to the extension-side chamber R1, and the shock absorber D generates a damping force that hinders the contraction operation.

[0056] On the other hand, when the shock absorber D is contracting, if the piston speed exceeds the low speed and becomes high, the pressure in the compression side chamber R2 reaches the valve opening pressure of the laminated leaf valve V, causing the laminated leaf valve V to bend and open, and the liquid passes through the compression side port 1c and then passes between the laminated leaf valve V and the seat portion 1e, moving from the compression side chamber R2 to the extension side chamber R1.

[0057] Therefore, when the shock absorber D is contracting and the piston speed is high, the stacked leaf valve V provides resistance to the flow of liquid from the compression-side chamber R2 to the extension-side chamber R1, and the shock absorber D generates a damping force that hinders the contraction operation.

[0058] As described above, when shock absorber D contracts, if the piston speed of shock absorber D is low, a damping force characteristic of a choke is generated, in which the damping force increases proportionally to the piston speed, and if the piston speed is high, a damping force characteristic of a leaf valve is generated, in which the rate at which the damping force increases with respect to the piston speed is smaller than at low speeds, but the damping force increases proportionally to the piston speed. As shock absorber D contracts, free piston 14 moves down in FIG. 1 in accordance with the volume of rod 11 entering cylinder 10, thereby reducing air chamber G and compensating for the volume of rod 11 entering cylinder 10.

[0059] Here, the arm portion 3c formed on the outer periphery of the communication hole 3a in the second leaf valve 3 of the stacked leaf valve V is provided with a weakened portion 3d formed by a notch 3e that opens at the circumferential end of the communication hole 3a and extends toward the periphery, thereby reducing the rigidity of the arm portion 3c and making the tip side of the arm portion 3c more likely to bend from the weakened portion 3d. Therefore, when the second leaf valve 3 is sandwiched between the first leaf valve 2 and the third leaf valve 4, the arm portion 3c can conform to the surfaces of the first leaf valve 2 and the third leaf valve 4 and fit tightly to the first leaf valve 2 and the third leaf valve 4. This prevents a gap from forming between the arm portion 3c and the first leaf valve 2 or the third leaf valve 4, preventing the communication hole 3a from being communicated with the expansion-side chamber R1 through any means other than the choke passage. Therefore, when the piston speed is low during expansion / contraction operation, the shock absorber D can generate the desired damping force through the choke passage.

[0060] As described above, the stacked leaf valve V of this embodiment is annular, with its outer periphery as a free end, allowing deflection on the free end side, and is stacked on a piston (valve seat member) 1 having a compression side port (port) 1c to open and close the compression side port (port) 1c. The stacked leaf valve V comprises: an annular first leaf valve 2 having a through hole 2a communicating with the compression side port (port) 1c; an annular second leaf valve 3 stacked on the anti-piston side (anti-valve seat side) that forms the back surface of the first leaf valve 2; and an annular third leaf valve 4 stacked on the anti-piston side (anti-valve seat side) that forms the back surface of the second leaf valve 3. The second leaf valve 3 comprises a plurality of communication holes 3a that are spaced apart in the circumferential direction and can communicate with the through hole 2a; a plurality of cutout passages 3b that open from the outer periphery that forms the free end and lead to the corresponding communication holes 3a; and fragile portions 3d that reduce the rigidity of arm portions 3c that are formed on the outer periphery of the communication holes 3a on both circumferential sides of the cutout passages 3b.

[0061] In the stacked leaf valve V configured in this manner, the arm portion 3c of the second leaf valve 3 has the fragile portion 3d that reduces the rigidity and makes it easy to bend and deform, and can tightly fit to both the first leaf valve 2 and the third leaf valve 4 without creating a gap between them, thereby preventing the communication hole 3a from communicating with the expansion-side chamber R1 through any route other than the choke passage. Therefore, since the arm portion 3c has the fragile portion 3d, it can tightly fit to both the first leaf valve 2 and the third leaf valve 4, and the circumferential length of each communication hole 3a in the second leaf valve 3 can be narrowed.

[0062] Furthermore, narrowing the circumferential width of each communication hole 3a makes it possible to shorten the circumferential length W of the arm portion 3c, as shown in Fig. 3. In this way, with the stacked leaf valve V of this embodiment, the circumferential length W of the arm portion 3c can be shortened, which prevents the arm portions 3c of adjacent second leaf valves 3, 3 from becoming entangled during transportation or storage of the second leaf valves 3, and reduces the effort required to separate the second leaf valves 3, 3, thereby reducing the workload when assembling the stacked leaf valve V. As described above, with the stacked leaf valve V of this embodiment, it is possible to improve assembly ease and obtain good choke characteristics.

[0063] Since the notched passage 3b forming the choke passage is always communicated with the communicating hole 3a, the arm portions 3c are formed on both sides of the notched passage 3b in the circumferential direction on the outer periphery of one communicating hole 3a. However, even if the weakened portion 3d is provided on only one of the pair of arms 3c, 3c on the outer periphery of one communicating hole 3a, one arm 3c can deform to conform to the first leaf valve 2 and the third leaf valve 4, thereby improving the degree of intimate contact of the other arm portion 3c with the first leaf valve 2 and the third leaf valve 4. Therefore, the weakened portion 3d may be provided on only one of the pair of arms 3c formed on both sides of the notched passage 3b on the outer periphery of one communicating hole 3a. Furthermore, since the radial width of the weakened portion 3d becomes narrower and the rigidity decreases as the length of the notch 3e is increased and the tip of the notch 3e approaches the outer periphery of the second leaf valve 3, the rigidity of the weakened portion 3d can be adjusted by the length of the notch 3e.

[0064] Furthermore, in the stacked leaf valve V of this embodiment, the fragile portion 3 d is formed by a notch 3 e that opens from the circumferential end of the communicating hole 3 a and extends toward the outer periphery, which is the free end side of the arm portion 3 c. With the stacked leaf valve V configured in this manner, the fragile portion 3 d can be formed without affecting the shape of the inner and outer peripheries of the second leaf valve 3, so that even with the fragile portion 3 d provided, the worker assembling the stacked leaf valve V can perform the assembly work without any discomfort.

[0065] In addition, to form the fragile portion 3d in the second leaf valve 3, other than providing a notch 3e that opens to the circumferential end of the communicating hole 3a, as in the first modified example of the stacked leaf valve V shown in Figure 4, a communicating hole 3a that has a wider radial width at the circumferential end relative to the second leaf valve 3 may be provided, thereby narrowing the radial width of the base end portion of the arm portion 3c1 on the outer periphery of the communicating hole 3a, and the base end portion of the arm portion 3c1 may be made into the fragile portion 3d1.

[0066] Alternatively, the fragile portion 3d2 may be formed by a notched groove 3f that opens from the outer periphery, which is the free end of the arm portion 3c, and extends toward the circumferential end of the communicating hole 3a, as in the second modified example of the stacked leaf valve V shown in FIG. 5 . According to the stacked leaf valve V configured in this manner, the notched groove 3f is provided in the second leaf valve 3 to form the fragile portion 3d2, thereby reducing the rigidity of the arm portion 3c, thereby achieving the desired choke characteristics and improving assembly by preventing the arms 3c from becoming entangled. The notched groove 3f may be provided so that, when viewed axially, its tip does not communicate with the communicating hole 3a and the through-hole 2a of the first leaf valve 2. Because the notched groove 3f is provided at a position that does not communicate with the through-hole 2a, it is sufficient to avoid the notched passage 3b and the communicating hole 3a. This allows for greater design freedom in the location and shape of the opening in the second leaf valve 3, and facilitates tuning the rigidity of the arm portion 3c.

[0067] Furthermore, the fragile portion 3d3 may be formed by a hole 3g provided in the arm portion 3c, as in the third modified example of the stacked leaf valve V shown in Fig. 6. With the stacked leaf valve V configured in this manner, the fragile portion 3d3 can be formed without affecting the shape of the inner and outer peripheries of the second leaf valve 3, so that even if the fragile portion 3d3 is provided, the worker assembling the stacked leaf valve V can perform the assembly work without any discomfort. Furthermore, the rigidity of the arm portion 3c can be easily adjusted by adjusting the number of holes 3g provided in one arm portion 3c and the opening area, so tuning the rigidity of the arm portion 3c is also easy.

[0068] The shock absorber D of this embodiment includes a cylinder (outer tube) 10, a rod 11 movably inserted into the cylinder (outer tube) 10 in the axial direction, a piston (valve seat member) 1 that is housed in the cylinder (outer tube) 10 and partitions the cylinder (outer tube) 10 into an expansion-side chamber (working chamber) R1 and a compression-side chamber (working chamber) R2 and that has a compression-side port (port) 1c, and a laminated leaf valve V that is laminated on the piston (valve seat member) 1. The shock absorber D configured in this manner can improve assembly ease and achieve good choke characteristics.

[0069] 1, the two working chambers are an expansion-side chamber R1 and a compression-side chamber R2, and the laminated leaf valve V is provided above the piston 1 serving as a valve seat member in FIG. 1, and the laminated leaf valve V is used as a valve that generates a compression-side damping force, but the laminated leaf valve V may be provided on both the expansion-side chamber side and the compression-side chamber side, or only on the compression-side chamber side, of the piston 1. Also, in the case where the shock absorber D is a twin-tube shock absorber that has an outer shell as an outer tube around the outer periphery of the cylinder and a reservoir between the cylinder and the outer shell, the valve case that separates the compression-side chamber and the reservoir may be used as a valve seat member, and the laminated leaf valve V may be provided to open and close a port of the valve case.

[0070] Furthermore, as described above, the stacked leaf valve V is configured so as to open outward, with the inner periphery as the fixed end and fixed to the small diameter portion 11a of the rod 11, and the outer periphery as the free end, allowing for bending on the free end side, but the stacked leaf valve V may also be configured so as to open inward, with the outer periphery as the fixed end and the inner periphery as the free end, allowing for bending on the inner periphery side. When the stacked leaf valve V is configured so as to open inward, the outer diameters of the stacked leaf valves V may be made uniform, the outer peripheries of the stacked leaf valves V may be fixed immovably to the valve seat member, and the notched passages may be opened from the inner periphery, which is the free end of the stacked leaf valve V, to communicate with the communication hole.

[0071] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims.

[0072] DESCRIPTION OF SYMBOLS 1: Piston (valve seat member), 1c: Compression side port (port), 2: First leaf valve, 2a: Through hole, 3: Second leaf valve, 3a: Communication hole, 3b: Notched passage, 3c, 3c1: Arm portion, 3d, 3d1, 3d2, 3d3: Weak portion, 3e: Notch, 3f: Notched groove, 3g: Hole, 4: Third leaf valve, 10: Cylinder (outer tube), 11: Rod, D: Shock absorber, V: Stacked leaf valve, R1: Expansion side chamber (operating chamber), R2: Compression side chamber (operating chamber)

Claims

1. A stacked leaf valve which is annular with either an inner or outer periphery as a free end, allowing deflection on the free end side, and is stacked on a valve seat member having a port to open and close the port, comprising: a first annular leaf valve having a through hole communicating with the port; a second annular leaf valve stacked on an anti-valve-seat side surface which forms the back surface of the first leaf valve; and a third annular leaf valve stacked on an anti-valve-seat side surface which forms the back surface of the second leaf valve, wherein the second leaf valve has a plurality of communication holes spaced apart in the circumferential direction and capable of communicating with the through holes, a plurality of notched passages which open from the free end and lead to the respective communication holes, and a weakened portion which reduces the rigidity of an arm portion formed on the outer periphery of the communication holes and on at least one side of the circumferential direction of the notched passage.

2. A laminated leaf valve as claimed in claim 1, wherein the fragile portion is formed by a notch opening from a circumferential end of the communication hole and extending towards the free end of the arm portion.

3. A laminated leaf valve as claimed in claim 1, wherein the fragile portion is formed by a notched groove opening from the free end side of the arm portion and extending towards the circumferential end of the communication hole.

4. A laminated leaf valve as claimed in claim 1, wherein said fragile portion is formed by a hole provided in said arm portion.

5. A shock absorber comprising: an outer tube; a rod inserted into said outer tube so as to be axially movable; a valve seat member housed within said outer tube to partition said outer tube into two working chambers and having a port; and a laminated leaf valve according to any one of claims 1 to 4 laminated on said valve seat member.

Images